The present invention relates to apparatus and method for treating carbon fiber fabrics and particularly to a disintegrating apparatus for a carbon fiber fabric obtained by using a multifilament yarn, namely, an apparatus for discretely separating carbon filaments bonded together with a sizing agent.
In molding a composite material which contains a woven texture of carbon fibers obtained by weaving a multifilament yarn, as a reinforcing member in a matrix resin, a step of disintegrating the filaments of the multifilament yarn as a step which precedes the molding step is known from Japanese Patent Laid Open No. 231073/1987. It is also disclosed therein to effect the disintegrating operation using ultrasonic wave. By the method using ultrasonic wave it is possible to greatly improve the strength of the composite material after molding, and the use of ultrasonic wave permits the individual filaments to be disintegrated in a more discrete state and also permits the effect of the method to be exhibited in a more satisfactory manner.
In order to practise the above method economically on an industrial scale it is necessary to use an apparatus for disintegrating the carbon fiber fabric continuously. This apparatus must be able to disintegrate the carbon fiber fabric efficiently and uniformly throughout the fabric into each constituent filament as completely as possible. Moreover, it is inevitably required that the cost of the apparatus itself and the running cost be low and that the operation as well as maintenance and control be easy.
It is the first object of the present invention to provide an apparatus particularly suitable for practising the disintegrating step using ultrasonic wave and capable of satisfying the above-mentioned requirements.
As to a sizing agent, if a fabric with a sizing agent adhered to the weaving yarn is impregnated with a matrix resin, the matrix resin is difficult to permeate the weaving yarn because a bundle of several hundred to several ten thousand filaments which constitute the weaving yarn is in a bonded state with the sizing agent. Therefore, it is desirable to remove the sizing agent from the fabric before the matrix impregnation.
As means for removing a sizing agent from a carbon fiber or glass fiber fabric there are known a heat setting method wherein the sizing agent is burnt off and a method wherein the sizing agent is removed using a solvent. In the heat setting method, however, there easily occur shift in weave and napping because the fabric is exposed to a high temperature, and if the sizing agent after decomposition and carbonization remains on the fiber surface, the reinforcing effect will be deteriorated markedly. The method using a solvent is also disadvantageous in that it usually requires the use of an expensive solvent so the cost is high and danger is involved therein and that the equipment required is large-sized.
Usually, therefore, a resin of the same sort as the matrix resin is used as the sizing agent to thereby omit the sizing agent removing step.
However, it is actually very troublesome to change the sizing agent according to the kind of the matrix resin used. Thermosetting resins typified by epoxy resins have heretofore been mainly used as the matrix of composite fiber-reinforced materials, but recently, in addition to epoxy and other thermosetting resins, various matrix resins have come to be used, including thermoplastic resins such as polyester, nylon and polyether ether ketone. Providing many kinds of sizing agents for such various matrix resins causes an increase of economic burden and gives rise to complicated problems in production management and inventory management. Such problems can be overcome if it is possible to inexpensively provide reinforcing yarn fabrics from which sizing agents have been removed. To this end it is necessary to find out a simple method for removing a sizing agent from a fiber-reinforced fabric.
It is the second object of the present invention to provide method and apparatus for removing a sizing agent from a reinforcing yarn fabric easily and efficiently.